the importance of this region in face processing came through the use of fMRI, which found that a region of the fusiform gyrus, the "fusiform face area", responded selectively to images of faces. Intracranial recordings in humans using electrocorticography provide very strong evidence that the fusiform face area is one of the generators of the N170, though other regions of the face processing network may also contribute to the N170. An investigation of the N170 undertaken used ERP source-localization techniques to estimate the location of the neural generator of the N170. They concluded that the N170 arose from the posterior superior temporal sulcus. However, these techniques are fraught with potential sources of error, and there is disagreement on the validity of inferences drawn from such findings. Faces or interstimulus variance In 2007, Guillaume Thierry and colleagues presented evidence that called into question the face-specificity of the N170. Most earlier experiments found an N170 when the response to frontal views of faces was compared to those of other objects that could appear in more variable poses and configurations. In their study, they introduced a new factor: stimuli could be faces or non-faces, and either class could have high or low similarity. Similarity was measured by calculating the correlation between pixel values in pairs of same-category stimuli. When ERPs were compared for these conditions, they found a typical N170 effect in the low-similarity non-face vs. high-similarity face comparison. However, high-similarity non-faces showed a significant N170, while low-similarity faces did not. These results led the authors to conclude that the N170 is actually a measure of stimulus similarity, and not face processing per se. In response to this, Rossion and Jacques measured similarity as above for several object categories used in a previous study of the N170. They found that faces elicited a larger N170 than other classes of objects that had similar or higher similarity values, such as houses, cars, and shoes. While it remains uncertain why Thierry et al. observed an effect of similarity on the N170, Rossion and Jacques speculate that lower similarity leads to more variance in the latency of the response. Since ERP components are measured by averaging the results from many individual trials, high latency variance effectively “smears” the response, reducing the amplitude of the average. Rossion and Jacques also offer criticism of the methodology used by Thierry and colleagues, arguing that their failure to find a